The head of the United Nations refugee agency (UNHCR) said on Thursday that fierce fighting in Pakistan's North West Frontier Province (NWFP) has displaced tens of thousands of residents and the agency has stepped up its humanitarian response to cope with the crisis. Pakistan's military launched a major offensive against Taliban forces in the Swat Valley region of the NWFP on Wednesday - an offensive that could displace some 500,000 people. “As part of the U.N. response, UNHCR is already sending humanitarian aid items to new camps that we are helping to set up in the Mardan and Swabi districts,” UNHCR head Antonio Guterres said in Geneva. “We are also assisting authorities to establish two new reception centers and two more are planned for newly displaced people on main routes adjacent to the conflict zone. We are also helping with their registration,” he said. “In addition to helping displaced Pakistanis, I am also deeply concerned over the well-being of some 20,000 registered Afghan refugees who have been affected by the conflict in the Buner, Lower Dir and Upper Dir regions,” Gutteres added. “We have reports that many have fled together with the local population. Some have chosen to return to Afghanistan with UNHCR assistance and others have chosen to relocate to existing refugee sites in Pakistan,” he said. The U.N. has warned that the fighting could result in a major humanitarian crisis. Before the latest displacement, the U.N. refugee agency had registered almost 600,000 internally displaced people from tribal areas and NWFP.